A raised-floor system is used where it is desirable to maintain ready access below the floor surface to cables, wiring, etc. Such access floor systems are used extensively in computer and control rooms. They have a discrete modular structure, made up of module floor panels which are supported above a base floor by a plurality of upright support columns. Raised-floor systems for computer rooms are, for example, disclosed in U.S. Pat. Nos. 5,467,609 A and 6,370,831 B1.
Normally, computers produce a considerable amount of heat, so that computer rooms have to be air-conditioned. The volume between the base floor and the raised floor of a raised-floor system can be used as a cooling air supply duct. Typically, the cooling air enters this volume at one side of the computer room and leaves the volume upwardly through floor panels with cooling air outlets distributed over the computer room (see, for example, JP 2002061911 A).
Usually, computers have to be connected to active network elements, such as routers and switches, with data transmission cables, in the form of copper cables or optical fiber cables. These data cables run below the raised floor so as to keep the surface of the raised floor free of obstacles in order to provide the operators free access to the computer equipment. An example of a raised-floor system with underfloor cable trays is disclosed in US 2002/0003194 A1.
Cabling a computer room uniquely for a particular computer configuration would be very inflexible. For example, if in a certain part of the computer room existing computers are replaced by computers requiring a different type of data cable or having a higher port density, existing data cables would have to be replaced (which is hardly possible) or additional data cables would have to be laid. Therefore, to enable a computer room to be used in a flexible way, computer rooms are usually equipped from the outset with a universal data cabling. For example, such a universal cabling includes as many copper cables and optical monomode and multimode fiber cables as required for all expected future computer configurations. The cables end at cable junction units which are distributed throughout the computer room. These data cables and their respective junction units are permanently installed and are not changed, even when the computer configuration is changed. The ports of each computer are connected to one or more nearby junction units by means of (normally flexible) patch cables. Only the patch cable cabling is changed when the computer configuration changes.
In raised-floor systems, data cable junction units are usually disposed below the surface of the raised floor. Underfloor junction boxes for use in general office areas are, for example, described in U.S. Pat. Nos. 5,673,522 A, 5,149,277, 5,340,326and JP 10028313 A. WO 98/322204 and JP 07087651 A disclose junction units with two rows of connectors.
A prior art underfloor cable junction unit used in computer room installations is shown in FIG. 8 which is a perspective view of a part of a computer room with a raised-floor system in which the floor panels are shown to be transparent. On a base floor 1, floor columns 2 support floor panels 3 which together form a raised floor 4. The raised-floor system is a modular system in which the floor panels 3 are typically in the form of squares, for example with the dimension of 60 cm×60 cm which rest on a square frame which in turn rests on the floor columns 2 arranged at the square corners. The height of the raised floor is typically 50 cm to 70 cm, but there are also installations of only about 30 cm. Computers 5 (only two of them are shown in FIG. 8) are placed on the raised floor 4.
Whereas the basic type of floor panel 3 has a completely closed surface, there are special floor panels with cooling air outlets 6 and floor panels with a cable aperture 7. Cooling air 8 flows in the volume under the raised floor 4 in a certain direction (from right to left in FIG. 8), and at each floor panel 3a some of the cooling air is branched off upwardly, flows through the cooling air outlets 6 and is partly sucked in by the nearby computers 5.
The room under the raised floor 4 also accommodates the cabling of the computer room. For example, in FIG. 8 bunches 9 of data cables run from a data communication room (not shown in FIG. 8) on the left-hand side of FIG. 8 on the base floor 1 from the left to the right in FIG. 8 (only one cable bunch 9 is shown in FIG. 8). The cable bunches comprise individual data cables 10 or bundles 12 of data cables which run in trough-like cable trays (not shown in FIG. 8) which define a cable route and thereby form the cable bunches 9. A plurality of underfloor cable junction units 11 are arranged throughout the computer room under the raised floor 4, one of which is illustrated in FIG. 8. The cable junction unit 11 is a closed box mounted on a support 13 closely below a floor panel 3 of the raised floor 4. The support 13 is C-shaped, wherein the lower leg 14 of the “C” is fixed to the base floor 1 and the junction unit 11 is mounted on the upper leg 15 of the “C”. The cable bunch 9 runs over the lower leg 14. The junction unit 11 has a cable bundle inlet 16 at one of its faces and a row 17 of connectors or ports 18 at either lateral side. In the example of FIG. 8, the junction unit 11 has two rows 17 of eight connectors 18, i.e. sixteen connectors or ports 18 in total. One of the cable bundles 12 branches off from the cable bunch 9 and runs upwardly to the cable bundle inlet 16. Inside the box-shaped junction unit 11, the cable bundle 12 is separated into individual cables 10 which are here connected to the cable connectors 18. If the cables 10 are copper cables, the cable connectors 18 are typically RJ45, RJ11, 25-pin sub-D, V35, X21, or RS232 connectors. If the cable bundle 9 is an optical bundle cable, the junction unit serves as a splice box, in which, upon installation, the optical bundle cable is separated into individual optical fibers, the ends of which are then manually spliced with the (optical) connectors 18 within the junction unit 11. The optical cable connectors are typically SC, ST, E2000, MTRJ or LC connectors.
The cabling described so far, is permanent, i.e. it is not changed when the configuration of computers 5 to be connected is changed. Rather, the part of the cabling which is adaptable to a particular computer configuration is constituted by patch cables 19 with suitable cable connectors 20 at both ends. The (typically flexible) patch cables 19 connect the connectors 18 with computer ports 21. They run from the junction units 11 below the raised floor 4, pass through the cable aperture 7 next to the computer 5 to be connected, and then run on the raised floor 4 to the computer 5.
Although junction units of the type described in FIG. 8 were considered sufficient in the past, there remains a need to provide an improved underfloor cable junction unit and computer centers equipped with such improved junction units.